The invention concerns a method for the closed-loop speed control of an internal combustion engine-generator unit.
Emergency standby installations are started in an uncoupled state when the public power supply system fails and are coupled with the generator, at the latest, when a rated speed is attained. A system of this type will be referred to hereinafter as an internal combustion engine-generator unit. In the case of electromagnetic couplings, the coupling process is initiated by a coupling signal. Couplings of this type usually already engage during the run-up of the internal combustion engine.
When the coupling engages, the total moment of inertia of the system experiences a sharp change. The internal combustion engine has a moment of inertia of about 20 kgm2. The generator with induction coupling has a moment of inertia of about 360 kgm2. After the power failure, the induction coupling supplies the necessary energy to the system until the internal combustion engine becomes available. The induction coupling thus represents an energy storage device. After the coupling engages, the induction coupling and the generator are driven by the internal combustion engine.
The internal combustion engine is delivered to the customer with a fixed standard set of parameters. This standard set of parameters must guarantee stable behavior for operation both with and without generator and induction coupling. Automatic control of the internal combustion engine is most difficult when the engine is uncoupled, i.e., the stability reserve is then at its lowest. Consequently, the standard set of parameters must be designed for the uncoupled case. This means that the internal combustion engine may be delivered with only a very small proportional coefficient and, if at all possible, without a D component. For all internal combustion engines that are operated with a generator, this means a loss of dynamic range. In the case of internal combustion engines that power systems with a very large moment of inertia, this is unsatisfactory.
The not previously published German patent application with the official file number DE 103 15 881.2 describes a method for the closed-loop speed control of an internal combustion engine-generator unit during a starting operation. In this method, a run-up ramp is selected as a function of a measured time interval to preset a set speed. Controller parameters for the determination of controller components of a speed controller are also selected as a function of this time interval. A proportional coefficient and an integral-action time are specified as controller parameters. The time interval corresponds to the time that an actual speed requires to pass through a speed range. The speed range begins at a starter speed, e.g., 300 rpm, and ends at a starting speed, e.g., 600 rpm. The method has proven effective in practice. However, it is critical that the parameters have already been established at the start of the run-up ramp. For the aforementioned example of a coupling that does not engage until during the run-up of the engine, this means that the starting operation is not being operated with the optimum parameters.